In order to investigate the effects of foliage plants on the thermal environment and comfort inside a room, experiments were carried out in two rooms with the same size in winter. Foiiage plants used in the experiments were Schefflera arboricola "Hong Kong" and Dracaena fragrans "Massangeana". In our previous experiments, the former showed the highest transpiration rate and the latter showed little transpiration. The following three experiments were performed. In the experiment R, S. arboricola "Hong Kong" plants were placed in line at the southern end in one room and no plant was placed in the other room. In the experiment R, S. arboricola "Hong Kong" plants were placed in line at the southern end in one room and D. fragrans "Massangeana" plants were placed in line at the southern end in the other room. In the experiment (D, S. arboricola "Hong Kong" plants were placed in line at the southern end in one room and interspersed in the other room. In the experiment (D, S. arboricola "Hong Kong" in line at the southern end in the room brought about an increase in air temperature of about l.S°C and an increase in relative humidity of more than 20%. In the experiment c, relative humidity in the room with S. arboricola "Hong Kong" in line at the southern end was 20% higher than that with D. fragrans "Massangeana". This effect is considered to be caused by higher transpiration of S. arboricola "Hong Kong". In the experiment (D, S. arboricola "Hong Kong" interspersed in the room showed the same increase in relative humidity as S. arboricola "Hong Kong" in line at the southern end in the room. Furthermore, MRT and PMV was calculated from the measured data. The MRT showed some difference between the two rooms in the experiment c and the experiment (3), but there was little difference between the PMV of the two rooms in the three experiments.
